The present invention relates to aerial lift platforms, or cranes, mounted on a wheeled chassis, and including a rotatable turret and linearly extending boom.
There have been provided cranes which comprise a chassis, and wheels or the like for engaging the ground and enabling the chassis to move over the ground. The chassis supports a generally linearly extending boom, and typically the boom is carried on a horizontal pivot that is supported by a rotatable turret, the turret being rotatable about a generally vertical axis. The boom may be telescopic, and, in a crane, has at its outer end a load support, such as blocks and a cable. Similar devices, known as aerial lift platforms, have provided a workman's platform or basket at or near the outer end of the boom, for supporting a workman at an elevated location. Both cranes and aerial lift platforms are capable of being positioned so that there is a substantial overturning moment. This overturning moment has been counteracted by counterweights, and by so-called outriggers. The outriggers may be caused to extend outwardly from the chassis, and to provide for engagement with the ground at a distance or spacing greater than that of the ground engaging wheels, or the like. Another provision for increasing the stability of such cranes and aerial lift platforms has been to provide the wheels with extendable axles, so that the wheels could be placed at relatively great distances from the chassis, to increase stability during operation of the crane or aerial lift platform, the wheels being retracted so as to be relatively closer to the chassis during transit.